1. Field of the Invention
The invention relates to a system for calculating thread pitches of screw threads formed on a workpiece by a machine tool which includes a rotary shaft and a feed shaft.
2. Description of the Related Art
A numerically controlled machining system is known which includes a rotary shaft for rotating a workpiece and a feed shaft for moving a tool for machining the workpiece and which calculates an error between an ideal movement amount and an actual movement amount of the feed shaft so as to evaluate the accuracy of the threading process by monitoring and verifying the error (for example, Japanese Laid-open Patent Publication No. 2008-226112).
According to prior art, since it has been impossible to understand the effect derived from the error between the ideal movement amount and the actual movement amount of the feed shaft by the thread pitches of the actually formed threads, it has been impossible to carry out comparative verification by correlating the actual thread pitches and the above-described error.
Accordingly, when there is an inappropriate fluctuation in the formed thread pitches, it has been difficult to judge whether the fluctuation is caused by a problem in controlling the rotary shaft and the feed shaft or caused by factors other than the control of the rotary shaft and the feed shaft.